全文获取类型
收费全文 | 104429篇 |
免费 | 2507篇 |
国内免费 | 497篇 |
专业分类
化学 | 58390篇 |
晶体学 | 1018篇 |
力学 | 3329篇 |
综合类 | 8篇 |
数学 | 15555篇 |
物理学 | 29133篇 |
出版年
2022年 | 626篇 |
2021年 | 922篇 |
2020年 | 1144篇 |
2019年 | 1002篇 |
2018年 | 1295篇 |
2017年 | 1238篇 |
2016年 | 2348篇 |
2015年 | 1807篇 |
2014年 | 2269篇 |
2013年 | 4894篇 |
2012年 | 4624篇 |
2011年 | 5455篇 |
2010年 | 3550篇 |
2009年 | 3215篇 |
2008年 | 4748篇 |
2007年 | 4622篇 |
2006年 | 4524篇 |
2005年 | 3994篇 |
2004年 | 3694篇 |
2003年 | 3078篇 |
2002年 | 2881篇 |
2001年 | 2673篇 |
2000年 | 2067篇 |
1999年 | 1700篇 |
1998年 | 1429篇 |
1997年 | 1453篇 |
1996年 | 1435篇 |
1995年 | 1311篇 |
1994年 | 1343篇 |
1993年 | 1249篇 |
1992年 | 1359篇 |
1991年 | 1186篇 |
1990年 | 1151篇 |
1989年 | 1064篇 |
1988年 | 1053篇 |
1987年 | 1018篇 |
1986年 | 952篇 |
1985年 | 1318篇 |
1984年 | 1340篇 |
1983年 | 1084篇 |
1982年 | 1161篇 |
1981年 | 1129篇 |
1980年 | 1091篇 |
1979年 | 1089篇 |
1978年 | 1087篇 |
1977年 | 1078篇 |
1976年 | 999篇 |
1975年 | 899篇 |
1974年 | 867篇 |
1973年 | 809篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
941.
Dmitrieva Z. T. Bondaletov V. G. Antonov I. G. Chernov E. B. 《Russian Journal of Applied Chemistry》2002,75(12):1951-1955
Kinetics of absorption of a mixture of aliphatic, aromatic, and unsaturated hydrocarbons from the gas phase onto polypropylene containing 5, 18, and 40% atactic polymer in its molecular lattice was studied. The kinetic parameters, equilibrium constant, and Gibbs energy of adsorption-desorption of the hydrocarbons were determined by zero-, first-, and second-order optimization of the solution of the multiparameter equation. These parameters were correlated with the adsorbent composition and the number of sorption-desorption cycles. 相似文献
942.
A. Vértes Z. Klenesár Gy. Vankó T. Marek K. Süvegh Z. Homonnay E. Kuzmann 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(1):241-253
The paper offers three applications of nuclear methods in the research of chemical structure. First, progress in positron annihilation spectroscopy is illustrated by a positron beamline study, which obtained results that are not available through conventional experiments. The positron beam was used for the study of Langmuir-Blodgett (LB) films containing 4-58 layers of arachidic acid and its salts. These measurements have shown that this emerging technique is capable of characterizing even such elusive systems. Second, the potential of Mössbauer spectroscopy to answer current challenges of solid state chemistry are shown in a study on perovskites of recent interest. 151Eu Mössbauer spectroscopy was used to study the effect of Pr substitution in EuBa2Cu3O7-. It was shown that the introduction of Pr into the rare earth site as well as into the Ba site results in the appearance of extra electrons both in the copper oxide planes and at the 4f shell of Eu cations. The observed effects were explained by the hole filling effect of Pr. Finally, a survey is presented on the recently developed techniques for nuclear resonant scattering of synchrotron radiation, an exciting and very rapidly developing extension to conventional Mössbauer spectroscopy. An interesting new result is that nuclear inelastic scattering experiments performed on solutions of 57Fe complexes show contribution from vibrations rather than from diffusion to the inelastic spectra. 相似文献
943.
944.
Yu. F. Zuev A. B. Mirgorodskaya L. A. Kudryavtseva B. Z. Idiyatullin R. N. Khamidullin 《Russian Journal of General Chemistry》2004,74(7):1051-1056
The structure of water/cetyltrimethylammonium bromide/n-butanol/hexane microemulsions was studied by conductometry, viscometry, and Fourier transform 1H NMR spectroscopy with pulse magnetic field gradient. The regions of phase inversion from inverse micelles in hexane through a bicontinual structure to a dispersion of normal micelles in water were determined. The influence of the structure of the microemulsions on the rate of hydrolysis of carboxylic acid p-nitrophenyl esters was analyzed. The hydrolysis rate constants considerably increase in going from inverse to normal microemulsions. 相似文献
945.
Komissarova N. L. Vol'eva V. B. Belostotskaya I. S. Kurkovskaya L. N. Starikova Z. A. 《Russian Journal of Organic Chemistry》2003,39(5):686-688
The Mannich reaction of 2,4-di-tert-butylphenol with dicyclohexylamine was found to involve formation of a stable 1:1 molecular complex between the phenol and amine. The complex does not change on melting, sublimation, and chromatography on silica gel. Its structure was determined by X-ray analysis. Stable 1:1 complexes of dicyclohexylamine with a series of substituted phenols were synthesized; exceptions were 2,6-disubstituted phenols with bulky substituents. 相似文献
946.
M. G. Koroleva O. V. Dyablo A. F. Pozharskii Z. A. Starikova 《Chemistry of Heterocyclic Compounds》2003,39(9):1161-1171
The previously unknown 1-amino- and 3-aminonaphtho[1,2-d]imidazoles, 1-aminonaphtho[2,3-d]imidazole, 1-aminophenanthro[9,10-d]imidazole and the N-amino-N'-methylimidazolium picrates corresponding to them have been obtained by direct amination of a series of condensed imidazoles with O-picrylhydroxylamine. An X-ray structural investigation of 1-amino-3-methylnaphtho[1,2-d]imidazolium picrate showed that, in difference to 1-aminobenzimidazolium salts, a conformation exists in it in which the hydrogen atoms of the N-NH2 group are directed to the side of the meso carbon atom. 相似文献
947.
Zelenin K. N. Verbov V. N. Matveeva Z. M. 《Chemistry of Heterocyclic Compounds》1977,13(12):1324-1327
It follows from the PMR spectra that the reaction of 1-methyl-, 1-phenyl-, 1-ethyl-,1-phenyl-, and 1,1-diphenyldiazenium salts with cis- and trans-d-styrenes, which leads to the corresponding 3-d-4-phenyl-1,2,3,4-tetrahydrocinnolines, takes place with retention of the configuration in the starting styrenes. It is therefore proposed that this reaction be regarded as a special case of [4+s + 2s]-cycloaddition.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1658–1661, December, 1977. 相似文献
948.
949.
Microchimica Acta - Mit der turbidimetrischen Strychninnitrat-Methode für Phosphorspurenbestimmung nach der Version von Hegedüs und Dvorszky kann man nur dann ausgezeichnete... 相似文献
950.
The application of internal reflection spectroscopy to the study of interface boundary layers has been extended over cases in which unstable particles appear at the interface as a result of imposing a negative electrical potential on the germanium hemicylinder, used simultaneously as an optical prism in the internal reflection spectroscopic device and as an electrode. The appearance of the particles is detected by their internal reflection spectrum. The method has been applied in the case of the electrochemically induced polymerization of acrylonitrile. Two particles were found to be generated during electrolysis. They are assigned to the anionradical and to the di-anion of acrylonitrile. 相似文献